TEST 4: Endocrine Flashcards
Endocrine System overview
(Lecture, p. 662)
-Is a collection of glands that secrete hormones—>
-Hormones are then passed thru the blood to a target organ, where they have cells with receptors that respond to the hormone—>
-That hormone- receptor interaction stimulates a chemical reaction in the target cells—>
-The cellular reaction control metabolism and maintain bodily homeostasis
The 5 main functions of the endocrine system
(P.662)
1.differentiation of the reproductive and CNS in developing fetus
2. Stimulation of sequential growth and development in childhood/ adolescence
3. Coordination of male and female reproductive systems
4. Maintenance of an optimal internal environment throughout life
5. Initiation of corrective and adaptive reprised when emergency demands occur
Functions of the endocrine system
(Lecture, p.662)
Regulates:
-growth and sexual maturation
- energy production and energy utilization by cells (metabolic rate)
-glucose homeostasis
-fluid and electrolyte balance
-circulatory function
Water and lipid soluble hormones
(Lecture, p. 663)
Water soluble:
-Interact with receptors proteins on the outside of a target cell and cause a cascade of events inside
-Are made from proteins, typically amino acids (soluble in water)
-Available in storage, transient effect
-Half life of seconds to minutes
-Ex = ADH, insulin, epi, growth hormone
Lipid soluble:
-Cross the cell membrane to reach the receptor inside the target cell and interact with the genes inside
-Are Steroid hormones made from cholesterol (soluble in FAT, not water)
-Made on demand )no reserve), persistent effect
-Half life of hours to days
-Ex = estrogen, androgen, steroids
Control of hormones
(Lecture, p. 662)
Negative feedback:
-Most common
-Occurs when an increase level of hormone inhibits further release
-“Hormone stops hormone”
Positive feedback:
-Surges of hormones
-Increased level of hormones stimulates further release
-“Hormone begets hormone”
Cyclic variations:
-Periodic variation in hormone release
-Ex= hormones related to menstruation, cortisol (circadian rhythm)
Mechanism of action for hormones
(Lecture, p. 664)
- Receptors:
-Number is up and down regulated by various stimuli - Intracellular signaling:
-Change membrane permeability, activates intracellular enzymes, and activate genes - Second messenger system:
-Mediates the effect of the hormone on the target cell - Action causing protein synthesis:
-Steroid hormones result in DNA transcription and protein synthesis
Hypothalamic- pituitary axis
(Lecture, p. 667)
-Forms the structural and functional basis for central integration of the neurologic and endocrine systems, creating the neuroendocrine system
Main hormones:
-ACTH
-ADH
-FSH
-LH
-TSH
Pituitary gland
(Lecture, p.667)
-Part of the hypothalamic- pituitary axis
-Located in Sella turnica (boney cavity at the base of the brain)
-Attached to the base of the brain (hypothalamus) by the pituitary stalk
-Two lobes: anterior and posterior pituitary
Anterior Pituitary
(Lecture, p. 668)
-Aka “adenohypophysis”
-Most pituitary hormones come from the anterior, including:
-Adenocorticotropin (ACTH or corticotropin) : controls secretions of adrenal cortex hormones
-Thyroid stimulating hormone (TSH or Thyrotropin) : controls secretions of thyroxine and triiodothyronine by thyroid gland
-Growth Hormone (GH)
-Prolactin (PRL) : promotes mammary gland development and lactation
-Follicle stimulating hormone (FSH)
-Luteinizing hormone (LH)
Hypothalamic hormones that control anterior pituitary secretion
(Lecture)
-Thyrotropin releasing hormone (TRH)
-Corticotropin releasing hormone (CRH)
-Growth hormone releasing hormone (GHRH)
-Growth hormone inhibitory hormone (GHIH or Somatostatin)
-Gonadotropic releasing hormone (GRH)
-prolactin inhibitory hormone (PIH)
Posterior pituitary 2 main hormones
(Lecture, p. 671)
- Antidiuretic hormone (ADH/ vasopressin): regulated water excretion as urine by the kidneys
- Oxytocin: facilitated milk expression during breast feeding/ role in uterine contraction and labor initiation and progression
Hypothalamic neurons secrete
(Lecture)
-Releasing and inhibitory hormones to regulate production
Growth hormone
(Lecture, p.671)
-Controls growth of body tissues
3 mechanisms used to grow tissue:
1. Increased mitosis
2. Cell differentiation
3. Cell hyper trophy
Metabolic effects:
increased protein synthesis, increased mobilization of fatty acids from adipose (ketosis), decreased rate of glucose metabolism by cells and decreases glucose utilization (conserves carbs)
Protein building:
enhances amino acid transport, increases transcription of DNA, enhances RNA translation and protein synthesis, decreases the breakdown of proteins and amino acids
Stimulates bone/ cartilage growth:
Increases deposition of protein by chondrocytic and osteogenic cells, increases rate of chondrocyte and osteocyte reproduction, induces conversion of chonrocytes to osteocytes for new bone deposition (cartilage can then convert to bone)
GEM most important role is in children converting cartilage to bone
Thyroid hormone synthesis mechanisms
(Lecture, p.673)
1.Iodides form dietary iodine are pumped from the blood into thyroid gland (TSH regulates the iodide pump activity based on concentration of circulating thyroid hormones)
2. Endoplasmic reticulum synthesizes thyroglobulin protein
3. Thyrotoxine (T4) and triiodothyroxine (T3) form from indication of tyrosine on the thyroglobulin
4. T3 and small amounts of T4 remain bound to thyroglobulin and are stored in gland follicles
5. Thyroid hormones are secreted from the follicles after cleavage from thyroglobulin by proteinases
6. TSH regulates the release of thyroid hormones
Physiologic function of thyroid hormone
(Lecture, p.673)
-Regulates protein, fat, carb metabolism
-Regulates cell metabolic rate
-Regulates body heat production
-Maintains growth hormone secretions and skeletal muscle maturation
-Affects CNS development (fetal-> 2 yo)
-Maintains cardiac rate, force, output
-Maintains secretions of GI tract
-Affects RR and oxygen utilization
*TSH is a negative feedback loop